ProCurve Switch xl Modules Installation Guide 2004-05

HP ProCurve Switch xl Modules

Mode Conditioning Patch Cord for Gigabit-LX

Mode Conditioning Patch Cord for Gigabit-

The following information applies to installations in which multimode fiber-optic

cables are connected to a Gigabit-LX port.

Unlike Gigabit-SX, which connects to only multimode fiber-optic cabling, Gigabit-

LX can use either single-mode or multimode cable. Multimode cable has a design

characteristic called “Differential Mode Delay”, which requires that the transmission

signals be “conditioned” to compensate for the cable design and thus prevent resulting

transmission errors. Since Gigabit-SX is designed to operate only with multimode

cable, Gigabit-SX mini-GBICs can provide that transmission conditioning internally.

Gigabit-LX mini-GBICs, since they are designed to operate with both single-mode

and multimode cable, do not provide the transmission conditioning internally. Thus,

under certain circumstances, depending on the cable used and the lengths of the cable

runs, an external Mode Conditioning Patch Cord may need to be installed between

the Gigabit-LX transmitting device and the multimode network cable to provide the

transmission conditioning.

If you experience a high number of transmission errors on the Gigabit-LX ports,

usually CRC or FCS errors, you may need to install one of these patch cords between

the Gigabit-LX port in your switch and your multimode fiber-optic network cabling,

and between the Gigabit-LX transmission device and the network cabling at the other

end of the multimode fiber-optic cable run. A patch cord must be installed at both

ends.

The patch cord consists of a short length of single-mode fiber cable coupled to graded-

index multimode fiber cable on the transmit side, and only multimode cable on the

receive side. The section of single-mode fiber is connected in such a way that it

minimizes the effects of the differential mode delay in the multimode cable.

Note Most of the time, if you are using good quality graded-index multimode fiber cable

that adheres to the standards listed on page 31, there should not be a need to use mode

conditioning patch cords in your network. This is especially true if the fiber runs in

your network are relatively short.

If you are using single-mode fiber-optic cabling in your network, there is no need to

use mode conditioning patch cords. Connect the single-mode network cable directly

to the Gigabit-LX mini-GBIC.